Cannot continue my model because of unexplained angles in the X Y and Z orientations
Try to change the transform orientation type to Global (in your case it is set to Normal).


You may also add a custom transformation for precise axes set up. Press Ctrl+Alt+Space and name it in the Transform Orientations panel of the Properties Shelf (N). In my case I filled the edge loop with a face (F) to set up the axes along its normal. Then added a custom transformation, deleted the face (X-->Faces) and extruded the edge loop along local Z axis (pressed E, then Z twice).


If the entire thumb moves while transforming it means, that you've enabled the proportional editing. Disable it.